CN215048708U - System for fly ash resourceful production high-purity alumina - Google Patents
System for fly ash resourceful production high-purity alumina Download PDFInfo
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Abstract
The utility model relates to a system of fly ash resourceful production high-purity alumina, this system includes along drawing the grinding machine that the alumina direction connected gradually, desiliconization reactor in advance, the activation is calcined the reactor, the acid leaching reactor, iron hydroxide purification reactor, neutralization reactor and high temperature calcination reactor, wherein, desiliconization reactor in advance still is connected with desiliconization agent doser in advance, the activation is calcined the reactor and still is connected with activator doser, the acid leaching reactor still is connected with the acid dip pickle doser, iron hydroxide purification reactor still is connected with iron hydroxide purification agent doser, neutralization reactor still is connected with neutralizer doser. Compared with the prior art, the utility model discloses, when realizing fly ash comprehensive utilization, realize the extraction of high-purity alumina and the hierarchical purification of edulcoration result, really realize the theory of solid useless resourceization.
Description
Technical Field
The utility model belongs to the technical field of environmental protection, a system for fly ash resourceful production high-purity alumina is related to.
Background
China is the largest coal producing and consuming country in the world and is also the largest producing country of the fly ash. Along with the rapid development of economy in China, the power demand is increasing day by day, and the emission of fly ash is also increased rapidly. In 2020 of China, the stockpiling amount of the fly ash reaches 30 hundred million tons. At present, the comprehensive utilization rate of the fly ash in China can reach 70%, but the actual utilization rate is less than 30%, and the industrial development has a plurality of problems. Because the fly ash is discharged for a long time and cannot be fully utilized, a large amount of fly ash is stockpiled, and the problem of serious environmental pollution is caused. At present, the wide use of the fly ash in China is still in the research and development stage, and the fly ash is regulated in the solid waste pollution environment prevention and control law of the people's republic of China, but the fly ash is treated as general solid waste, but the directive law and regulation are lacked to supervise and control the fly ash. Therefore, the resource utilization of the fly ash in China is far behind that in developed countries. Although China has started to adjust the energy structure, thermal power generation is still the main power source of China in the coming decades, and the problem of comprehensive utilization of fly ash is one of the environmental problems which are urgently needed to be solved currently and in the future in China.
The fly ash is a key point for environmental protection due to complex components and difficult treatment and disposal, but meanwhile, the fly ash has unique physicochemical properties and is rich in various valuable metal elements, so that reasonable resource utilization is urgently needed as a potential resource. At present, the fly ash is applied to the production fields of building materials, ceramics and the like, but the high-valued utilization rate is low. In recent years, the extraction of valuable elements in fly ash has been taken as a high-value utilization way, and becomes a research hotspot of domestic and foreign scholars. Especially, the extraction of aluminum can not only solve the problem of the accumulation of the fly ash, but also effectively utilize a large amount of aluminum resources in the ash. In the extraction process, because the alumina in the fly ash mainly exists in the form of stable crystalline substances such as mullite, corundum and the like, the SiO in the fly ash is difficult to directly destroy by adopting a common extraction process2-Al2O3Bonds and mullite structure. In addition, because the phase composition of the fly ash is extremely complex, the impurity removal process in the extraction process needs to be improved.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a system for fly ash resourceful production high-purity alumina, when realizing fly ash comprehensive utilization, realize the extraction of high-purity alumina and the hierarchical purification of edulcoration result, really realize the theory of solid useless resourceful.
The purpose of the utility model can be realized through the following technical scheme:
one of the technical scheme of the utility model provides a system of fly ash resourceful production high-purity alumina, include along the machine that grinds that draws the alumina direction to connect gradually, desiliconization reactor in advance, the activation is calcined the reactor, the acid leaching reactor, ferric hydroxide purification reactor, neutralization reactor and high temperature calcination reactor, wherein, desiliconization reactor still is connected with desiliconization agent doser in advance, the activation is calcined the reactor and still is connected with activator doser, the acid leaching reactor still is connected with the acid dip liquid doser, the ferric hydroxide purification reactor still is connected with the ferric hydroxide and carries the pure agent doser, neutralization reactor still is connected with the neutralizer doser.
Further, a liquid outlet of the pre-desiliconization reactor is also connected with a calcium silicate purification reactor, the calcium silicate purification reactor is also connected with a silicon removing agent doser, and a liquid outlet of the calcium silicate purification reactor is also connected with the pre-desiliconization reactor in a return way. Furthermore, a second sedimentation tank is arranged between the calcium silicate purification reactor and the pre-desilication reactor.
Furthermore, a screen machine is arranged between the grinder and the pre-desilication reactor, wherein a coarse powder outlet of the screen machine is also connected with an inlet of the grinder in a returning way.
Further, along the direction of extracting the alumina, a first sedimentation tank is arranged between the pre-desilication reactor and the activation calcination reactor, a third sedimentation tank is arranged between the acid leaching reactor and the ferric hydroxide purification reactor, a fourth sedimentation tank is arranged between the ferric hydroxide purification reactor and the neutralization reactor, and a fifth sedimentation tank is arranged between the neutralization reactor and the high-temperature calcination reactor.
Further, the liquid outlet of the neutralization reactor is also connected with the inlet of the ferric hydroxide purification reactor in a return mode.
The second technical scheme of the utility model provides a method for producing high-purity alumina by using fly ash as a resource, which comprises the following steps:
(1) adding the fly ash to be treated into a grinder for grinding treatment, sieving to obtain fine powder particles, discharging the fine powder particles into a pre-desiliconization reactor, adding a pre-desiliconization agent for pre-desiliconization treatment, and discharging precipitates into an activation calcination reactor after solid-liquid separation of sludge-water mixed liquid after treatment;
(2) adding an activating agent into the activation and calcination reactor, performing activation and calcination treatment, and discharging the obtained calcination product into an acid leaching reactor;
(3) adding acid leaching solution into the acid leaching reactor for acid leaching reaction, settling and separating the obtained reaction product, and discharging the supernatant into an iron hydroxide purification reactor;
(4) adding an iron hydroxide purifying agent into the iron hydroxide purifying reactor for purification treatment, precipitating and separating the treated mixed solution, and continuously discharging the obtained supernatant into a neutralization reactor;
(5) adding a neutralizing agent into the neutralization reactor to continuously adjust the pH, then settling and separating to obtain an aluminum hydroxide precipitate, and discharging the aluminum hydroxide precipitate into the high-temperature calcination reactor;
(6) and (3) carrying out high-temperature calcination on the aluminum hydroxide precipitate fed into the high-temperature calcination reactor to obtain the high-purity aluminum oxide.
Further, in the step (1), the reaction time of the pre-desiliconization treatment is 30-1000 min.
Further, in the step (2), the temperature of the activation calcination is 100-1500 ℃, and the time is 10-500 min.
Further, in the step (3), the temperature of the acid dissolution reaction is 25-100 ℃, and the time is 30-600 min.
Further, in the step (4), the time of the purification treatment is 30-500 min.
Further, in the step (6), the temperature of the high-temperature calcination is 400-.
Further, the pre-desiliconization agent is one or more of sodium hydroxide, calcium oxide or potassium hydroxide.
Further, the activating agent is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate, and the adding amount of the activating agent is 10-300 g/L.
Further, the pickle liquor is one or more of hydrochloric acid, sulfuric acid, nitric acid or oxalic acid.
Further, the iron hydroxide purifying agent is one or more of sodium hydroxide, potassium hydroxide, calcium oxide, sodium bicarbonate or sodium carbonate.
Further, the neutralizing agent is one or more of hydrochloric acid, sulfuric acid, nitric acid or oxalic acid.
Further, in the step (1), the supernatant obtained by carrying out solid-liquid separation on the sludge-water mixed solution is subjected to desiliconization and then returns to the inlet of the pre-desiliconization reactor.
Further, in the step (2), the supernatant obtained after adjusting the pH and settling separation in the neutralization reactor is also refluxed to the inlet of the ferric hydroxide purification reactor.
Compared with the prior art, the utility model has the advantages of it is following:
(1) the process has strong universality, can extract alumina by high-value utilization aiming at the circulating fluidized bed fly ash or pulverized coal furnace fly ash, and the extraction rate of the alumina is not lower than 86 percent.
(2) The process realizes the high-efficiency removal, separation and purification of impurities through the processes of pre-desiliconization, deep desiliconization, fractional precipitation and the like, relieves the pressure of treatment and disposal of the solid waste of the coal-fired power plant coal ash, and realizes the complete resource utilization of the coal ash.
(3) The alkali liquor generated by the calcium silicate purification reactor and the neutralization reactor is refluxed, so that the generation of waste liquid is avoided, and the zero emission of the aluminum extraction process of the fly ash is realized.
(4) The calcium silicate, silica gel, ferric hydroxide and other products produced in the extraction process have high purity, the calcium silicate can be recycled as a heat-insulating material, the silica gel can be recycled as a high-activity adsorption material, and the ferric hydroxide can be recycled as a raw material of a pigment or a water purifying agent. And no secondary solid waste is generated in the extraction process of the alumina, so that the high-value utilization of the fly ash is really realized.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a diagram of the recovered calcium silicate, silica gel, iron hydroxide and aluminum oxide products of example 2;
FIG. 3 shows the results of optimizing the reaction conditions of the fly ash pre-desilication process and the calcium silicate extraction process;
FIG. 4 shows the results of reaction condition optimization in the pre-desiliconized fly ash activation calcination process and the acid leaching process.
The notation in the figure is:
1-a grinder, 2-a screen machine, 3-a pre-desilication reactor, 4-a first sedimentation tank, 5-a calcium silicate purification reactor, 6-a second sedimentation tank, 7-an activation calcination reactor, 8-an acid leaching reactor, 9-a third sedimentation tank, 10-an iron hydroxide purification reactor, 11-a fourth sedimentation tank, 12-a neutralization reactor, 13-a fifth sedimentation tank, 14-a high-temperature calcination reactor, 15-a pre-desilication agent doser, 16-a desilication agent doser, 17-an activator doser, 18-an acid leaching solution doser, 19-an iron hydroxide purification agent doser and 20-a neutralizer doser.
Detailed Description
The system for producing high-purity alumina by recycling fly ash of the utility model is explained in detail firstly.
In the description of the present invention, it is noted that the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
For really realizing solid useless resourceization, the utility model provides a system for fly ash resourceful production high-purity alumina, its structure is referred to shown in figure 1, include along drawing the grinding machine 1 that the alumina direction connected gradually, desiliconization reactor 3 in advance, activation calcination reactor 7, acid leaching reactor 8, ferric hydroxide purification reactor 10, neutralization reactor 12 and high temperature calcination reactor 14, wherein, desiliconization reactor 3 still is connected with desiliconization agent doser 15 in advance, activation calcination reactor 7 still is connected with activator doser 17, acid leaching reactor 8 still is connected with acid leaching liquid doser 18, ferric hydroxide purification reactor 10 still is connected with ferric hydroxide purification agent doser 19, neutralization reactor 12 still is connected with neutralizer doser 20.
The utility model provides a grind machine 1 is the equipment that grinds the material that commonly uses in this field, and in addition, it sieves "thin", "thick" in fine powder grain and the coarse powder grain that obtains after grinding relatively speaking to in order to distinguish, specific particle diameter scope is decided according to the actual demand.
In some embodiments, the liquid outlet of the pre-desilication reactor 3 is further connected to a calcium silicate purification reactor 5, the calcium silicate purification reactor 5 is further connected to a desiliconization agent doser 16, and the liquid outlet of the calcium silicate purification reactor 5 is further connected back to the pre-desilication reactor 3. Furthermore, a second sedimentation tank 6 is arranged between the calcium silicate purification reactor 5 and the pre-desilication reactor 3.
In some embodiments, a screen 2 is further disposed between the grinder 1 and the pre-desilication reactor 3, wherein the coarse powder outlet of the screen 2 is also connected back to the inlet of the grinder 1. The mesh number of the screen on the screen machine 2 can be designed to be 5-1500 meshes according to actual requirements.
In some embodiments, a first sedimentation tank 4 is further arranged between the pre-desilication reactor 3 and the activation calcination reactor 7, a third sedimentation tank 9 is further arranged between the acid leaching reactor 8 and the ferric hydroxide purification reactor 10, a fourth sedimentation tank 11 is further arranged between the ferric hydroxide purification reactor 10 and the neutralization reactor 12, and a fifth sedimentation tank 13 is further arranged between the neutralization reactor 12 and the high temperature calcination reactor 14 along the direction of extracting alumina.
In some embodiments, the liquid outlet of the neutralization reactor 12 is also connected back to the inlet of the ferric hydroxide purification reactor 10.
The method for producing high-purity alumina by recycling fly ash of the present invention is explained in the following.
Based on the system, the utility model also provides a method for producing high-purity alumina by recycling fly ash, the specific flow can be seen in figure 1, and the method comprises the following steps:
(1) adding the fly ash to be treated into a grinder 1 for grinding treatment, sieving to obtain fine powder particles, discharging the fine powder particles into a pre-desiliconization reactor 3, adding a pre-desiliconization agent for pre-desiliconization treatment, and discharging precipitates into an activation calcination reactor 7 after solid-liquid separation of sludge-water mixed liquid after treatment;
(2) adding an activating agent into the activation and calcination reactor 7, performing activation and calcination treatment, and discharging the obtained calcination product into an acid leaching reactor 8;
(3) adding acid leaching solution into the acid leaching reactor 8 for acid leaching reaction, settling and separating the obtained reaction product, and discharging the supernatant into an iron hydroxide purification reactor 10;
(4) adding an iron hydroxide purifying agent into the iron hydroxide purifying reactor 10 for purification treatment, precipitating and separating the treated mixed solution, and continuously discharging the obtained supernatant into a neutralization reactor 12;
(5) adding a neutralizing agent into the neutralization reactor 12 to continuously adjust the pH, then settling and separating to obtain an aluminum hydroxide precipitate, and discharging the aluminum hydroxide precipitate into the high-temperature calcination reactor 14;
(6) and (3) carrying out high-temperature calcination on the aluminum hydroxide precipitate fed into the high-temperature calcination reactor 14 to obtain the high-purity aluminum oxide.
In some embodiments, in step (1), the reaction time of the pre-desilication treatment is 30 to 1000 min.
In some embodiments, in step (2), the temperature of the activation calcination is 100-1500 ℃, and the time is 10-500 min.
In some embodiments, in step (3), the temperature of the acid dissolution reaction is 25 to 100 ℃ for 30 to 600 min.
In some embodiments, in step (4), the time of the purification treatment is 30 to 500 min.
In some embodiments, in step (6), the temperature of the high-temperature calcination is 400-1500 ℃, and the time is 10-300 min.
In some embodiments, the pre-desiliconization agent is one or more of sodium hydroxide, calcium oxide or potassium hydroxide, and the pre-desiliconization agent is added in the form of solution or slurry, corresponding to 5-50% by mass, and corresponding to 5-1000g of fly ash, with the addition amount of 100-. The pre-desiliconization agent is preferably calcium hydroxide or sodium hydroxide, mixed with calcium oxide or calcium hydroxide.
In some embodiments, the activating agent is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate, and the mass ratio of the activating agent to the precipitate obtained after the pre-desilication is 0.5-3.0.
In some embodiments, the acid leaching solution is one or more of hydrochloric acid, sulfuric acid, nitric acid or oxalic acid, the mass percentage is 5% -20%, the amount of the acid leaching solution corresponds to 5-1000g of fly ash, and the addition amount of the fly ash is 100-50000 mL.
In some embodiments, the iron hydroxide purifying agent is one or more of sodium hydroxide, potassium hydroxide, calcium oxide, sodium bicarbonate or sodium carbonate, and the dosage is 5-100g/L, wherein 5-100g of the iron hydroxide purifying agent is added to 1L of the supernatant obtained in the step (3).
In some embodiments, the neutralizing agent is one or more of hydrochloric acid, sulfuric acid, nitric acid or oxalic acid, and the dosage is 5-200 g/L.
In some embodiments, in step (1), the supernatant obtained by subjecting the slurry-water mixed solution to solid-liquid separation is subjected to desiliconization and then returned to the inlet of the pre-desiliconization reactor 3. The treatment time in the silicon removal treatment is 10-500min, the silicon removal agent is one or more of calcium oxide, calcium hydroxide, calcium chloride or calcium fluoride, and the adding amount is 5-200 g/L.
In some embodiments, in step (2), the supernatant obtained after adjusting the pH and settling separation in the neutralization reactor 12 is also refluxed to the inlet of the ferric hydroxide purification reactor 10.
The reaction principle of each part of the utility model is as follows:
1) a pre-desilication stage: firstly, primarily removing impurity silicon in the fly ash, adding strong alkali to dissolve part of silicon dioxide, and adding calcium salt to obtain high-purity calcium silicate. The reaction formulas are shown in (1) to (3).
2) And (3) calcining and activating stage: the mullite in the fly ash can be converted into nepheline by adding the activating agent and calcining at high temperature, so that the activity is greatly improved, the difficulty in subsequent aluminum extraction is reduced, and the extraction rate of aluminum is improved. The reaction formulas are shown in (4) to (8).
3Na2CO3+Al6Si2O13→NaAlSiO4+4NaAlO2+3CO2 (4)
SiO2+Na2CO3→2NaSiO3+CO2↑ (5)
Al2O3+Na2CO3→2NaAlO2+CO2↑ (6)
Fe2O3+Na2CO3→Na2O·Fe2O3+CO2↑ (7)
4Fe3O4+6Na2CO3+O2→6Na2O·Fe2O3+6CO2↑ (8)
3) And (3) silica gel purification stage: the addition of acid dissolves and activates the calcined nepheline and iron oxide, thereby obtaining a silicic acid colloid with higher purity. The reaction formulas are shown in (9) to (11).
2NaAlSiO4+8H+→2H2SiO3↓+2Na++2Al3++2H2O (9)
Na2O·Fe2O3+8H+→2Na++Fe3++4H2O (11)
3) And (3) iron hydroxide purification stage: the addition of alkali can directly convert aluminum ions into metaaluminate ions, and convert iron ions into ferric hydroxide precipitates for recycling.
2Fe3++6OH-→2Fe(OH)3↓ (13)
4) And (3) a neutralization reaction stage: acid is added to the solution to adjust the pH to about 8, which converts the meta-aluminate to an aluminum hydroxide precipitate.
5) And (3) an alumina extraction stage: the aluminum hydroxide precipitate is roasted at high temperature to obtain high-purity aluminum oxide.
2Al(OH)3→Al2O3+3H2O(g) (15)
In order to illustrate the examples of the present invention or the implementation method in the prior art more clearly, the following is a brief description of the examples and the flame retardant property of the desulfurization waste water desulfurization precipitate, and the examples and the drawings in the following description are only some examples of the present invention, and for those skilled in the art, other examples or drawings can be obtained according to the drawings without any inventive labor.
Example 1:
a system and a method for producing high-purity aluminum oxide by recycling fly ash are shown in an extraction flow of figure 1, and comprise a grinder 1, a screen machine 2, a pre-desiliconization reactor 3, a first sedimentation tank 4, a calcium silicate purification reactor 5, a second sedimentation tank 6, an activation calcination reactor 7, an acid leaching reactor 8, a third sedimentation tank 9, an iron hydroxide purification reactor 10, a fourth sedimentation tank 11, a neutralization reactor 12, a fifth sedimentation tank 13 and a high-temperature calcination reactor 14 which are connected in sequence. Wherein, the pre-desiliconization reactor 3 is also connected with a pre-desiliconization agent doser 15, the calcium silicate purification reactor 5 is also connected with a desiliconization agent doser 16, the activation calcination reactor 7 is also connected with an activating agent doser 17, the acid leaching reactor 8 is also connected with an acid leaching solution doser 18, the iron hydroxide purification reactor 10 is also connected with an iron hydroxide purification agent doser 19, and the neutralization reactor 12 is also connected with a neutralizer doser 20.
The method comprises the following specific steps:
(1) adding the fly ash to be treated into a grinder 1 for grinding, then sending the fly ash into a screening machine 2, discharging fine powder particles which are screened and separated by the screening machine into a pre-desiliconization reactor 3, and discharging coarse powder particles back to the grinder 1 for continuous grinding;
(2) adding a pre-desiliconization agent into the pre-desiliconization reactor 3 for pre-desiliconization, performing solid-liquid separation on the sludge-water mixed solution after treatment in a first sedimentation tank 4, discharging the obtained precipitate into an activation and calcination reactor 7 for activation and calcination, discharging the supernatant into a calcium silicate purification reactor 5, adding a desiliconization agent, performing precipitation and separation in a second sedimentation tank 6, and refluxing the supernatant into the pre-desiliconization reactor 3, wherein the precipitate is a calcium silicate solid;
(3) after an activating agent is added into the activation calcining reactor 7, calcining and activating the mixture, converting mullite in the fly ash into nepheline, improving the activity of the nepheline so as to promote the subsequent leaching of aluminum, and discharging calcined products into an acid leaching reactor 8;
(4) adding acid leaching solution into the acid leaching reactor 8 for acid leaching reaction, settling and separating the acid leaching solution in a third sedimentation tank 9, discharging supernatant into an iron hydroxide purification reactor 10, and obtaining precipitate which is silica gel;
(5) adding an iron hydroxide purifying agent into an iron hydroxide purifying reactor 10 for reaction, and discharging supernatant into a neutralization reactor 12 after settling separation in a fourth settling pond 11, wherein the precipitate is iron hydroxide;
(6) adding a neutralizer into the neutralization reactor 12 to continuously adjust the pH, precipitating and separating through a fifth sedimentation tank 13, refluxing the supernatant to the ferric hydroxide purification reactor 10, discharging the aluminum hydroxide precipitate into a high-temperature calcination reactor 14, and calcining to obtain a high-purity aluminum oxide product.
Example 2:
on the basis of the alumina extraction process of example 1, the operating process parameters of this example are as follows:
TABLE 1 fly ash chemical composition of certain power plant of inner Mongolia
| Chemical composition | Al2O3 | SiO2 | Fe2O3 | CaO | MgO | Na2O | K2O |
| Wt％ | 29.64 | 48.26 | 5.54 | 9.66 | 1.20 | 1.44 | 0.90 |
The fly ash to be treated was taken from a coal fired power plant in inner Mongolia and its chemical composition is shown in Table 1. According to X-ray fluorescence spectrum analysis (XRF), the fly ash belongs to low-aluminum high-calcium fly ash.
In this example, 30g of fly ash treated by a grinder 1 and a screen 2 was weighed, wherein the screen 2 had a mesh size of 200 mesh (80 μm). The reaction time in the pre-desiliconization reactor 3 is 60min, the used pre-desiliconization agent is 600mL of sodium hydroxide with the mass fraction of 20%, the supernatant is discharged into the calcium silicate purification reactor 5 after the sedimentation separation in the second sedimentation tank 4, the reaction time is 30min, the used calcium silicate purification agent is calcium oxide, the adding amount is 20g/L, the supernatant flows back to the inlet of the pre-desiliconization reactor 3 after the sedimentation separation in the second sedimentation tank 6, the obtained calcium silicate precipitate can be recycled as a heat insulation product, and the comparison of various measurement indexes of the calcium silicate precipitate and the national standard calcium silicate heat insulation product (GB/T10699 2015) is shown in Table 2.
TABLE 2 calcium silicate insulation articles determination index comparison
| Index (I) | Calcium silicate product | GB/T 10699-2015 |
| Density (kg/m)3) | 213 | ≤240 |
| Average compressive Strength (MPa) | 0.69 | ≥0.65 |
| Average flexural strength (MPa) | 0.37 | ≥0.33 |
| Thermal conductivity (100 ℃, W/(m.K)) | 0.043 | ≤0.065 |
| Mass water content (%) | 2.34 | ≤7.5 |
| Dimensional stability (%) | 0.8 | ≤1.0 |
| Linear shrinkage (%) | 1.7 | ≤2.0 |
The pre-desiliconized fly ash sediment generated in the second sedimentation tank 4 is sent into an activation calcination reactor 7, the reaction time is 120min, the used activating agent is sodium carbonate, and the mass ratio of the added amount of the sodium carbonate to the pre-desiliconized fly ash sediment is 1.2: 1. After calcination, the activated product is fed to an acid bath 8.
TABLE 3 comparison of silica gel desiccant determination indexes for packaging
| Index (I) | Silica gel product | GB 10455-1989 |
| Content (including structural Water,%) | 98.2 | ≥98 |
| pH | 4.3 | 4-8 |
| Specific resistance (omega cm) | 2740 | ≥2000 |
| Loss on drying (%) | 2.3 | ≤2.5 |
The reaction time in the acid leaching tank 8 is 30min, the used acid leaching solution is 200mL of 1mol/L sulfuric acid, the leaching of the sulfuric acid can remove the residual impurity silicon in the form of silicic acid colloid, after the silicon is settled and separated in the third sedimentation tank 9, the supernatant is discharged into the ferric hydroxide purification reactor 10, the obtained silica gel precipitate can be used as silica gel drying agent for resource recovery, and the determination indexes of the silica gel precipitate and the national standard silica gel drying agent for packaging (GB 10455-.
The water discharged from the third sedimentation tank 9 enters an iron hydroxide purification reactor 10, the reaction time is 25min, the used iron hydroxide purification agent is sodium hydroxide, the adding amount is 5g/L, after sedimentation separation in a fourth sedimentation tank 11, the supernatant is discharged into a neutralization reactor 12, and the obtained precipitate is iron hydroxide.
And the effluent of the fourth sedimentation tank 11 enters a neutralization reactor 12, the reaction time is 30min, the used neutralizing agent is hydrochloric acid, the adding amount of the hydrochloric acid is 80g/L, after sedimentation separation in a fifth sedimentation tank 13, the supernatant liquid flows back to an iron hydroxide purification reactor 10, and the obtained precipitate is aluminum hydroxide.
The aluminum hydroxide precipitate generated in the fifth sedimentation tank 13 is discharged into the high-temperature calcination reactor 14, the reaction time is 90min, the calcination temperature is 1200 ℃, the calcination product is high-purity aluminum oxide, and the indexes of the high-purity aluminum oxide are shown in the comparison table 4 with the national standard of aluminum oxide (GB/T24487-2009).
TABLE 4 comparison of alumina measurement indices
| Chemical composition (wt%) | Alumina product | GB/T 24487-2009 |
| Al2O3 | 98.6 | ≥98.4 |
| SiO2 | 0.04 | ≤0.06 |
| Fe2O3 | 0.01 | ≤0.03 |
| Na2O | 0.59 | ≤0.7 |
| Burn and relieve | 0.9 | ≤1.0 |
Fig. 2 is a diagram of recovered calcium silicate, silica gel, iron hydroxide and alumina products, and it can be seen from the diagram that each product recovered by the process has better quality, and can simultaneously extract other various high-value byproducts on the basis of realizing alumina extraction, thereby realizing high-value utilization of fly ash.
Fig. 3 is an experimental result of optimization of partial reaction conditions in the pre-desilication reactor and the calcium silicate purification reactor, and by optimizing the dosage of the pre-desilication agent (fig. 3(a)), the silica in the fly ash can be primarily dissolved out to the maximum extent, the loss of aluminum in the pre-desilication process can be reduced, and the influence of the loss on the subsequent purification process can be reduced. By optimizing the amount of calcium silicate purifying agent to be added (fig. 3(b)), it is possible to extract calcium silicate while ensuring the purity of the silicon product.
Fig. 4 shows the results of an optimization experiment of the reaction conditions in the activation calcination reactor 7 and the acid leaching reactor 8, and the optimal reaction conditions were established by examining the influence of the reaction temperature, the reaction time, and the amount of the added activator on the leaching effect of the subsequent alumina acid leaching (fig. 4 (a)). By examining the influence of the concentration of the pickle liquor, the pickle liquor temperature and the pickle liquor time on the alumina leaching effect (figure 4(b)), the maximum leaching of alumina in the pickle liquor reactor is ensured.
Example 3:
compared to example 2, most of them are the same, except that in this example: fly ash to be treated was taken from a power plant in the Shanghai and its chemical composition is shown in Table 5. According to X-ray fluorescence spectrum analysis (XRF), the fly ash belongs to high-aluminum low-calcium fly ash.
TABLE 5 fly ash chemical composition of certain power plant in Shanghai
| Chemical composition | Al2O3 | SiO2 | Fe2O3 | CaO | MgO | TiO2 | K2O |
| Wt％ | 39.73 | 50.67 | 3.86 | 2.48 | 0.533 | 1.44 | 0.788 |
In this example, 30g of fly ash treated by a grinder 1 and a screen 2 were weighed, wherein the screen 2 had a mesh size of 400 mesh (40 μm). The reaction time in the pre-desiliconization reactor 3 is 50min, the used pre-desiliconization agent is 600mL of sodium hydroxide with the mass fraction of 15%, the supernatant is discharged into the calcium silicate purification reactor 5 after the sedimentation separation in the second sedimentation tank 4, the reaction time is 25min, the used calcium silicate purification agent is calcium hydroxide, the adding amount is 25g/L, the supernatant flows back to the inlet of the pre-desiliconization reactor 3 after the sedimentation separation in the second sedimentation tank 6, the obtained calcium silicate precipitate can be recycled as a heat insulation product, and the comparison of various measurement indexes of the calcium silicate precipitate and the national standard calcium silicate heat insulation product (GB/T10699-2015) is shown in Table 6.
TABLE 6 calcium silicate insulation articles determination index comparison
| Index (I) | Calcium silicate product | GB/T 10699-2015 |
| Density (kg/m)3) | 232 | ≤240 |
| Average compressive Strength (MPa) | 0.67 | ≥0.65 |
| Average flexural strength (MPa) | 0.34 | ≥0.33 |
| Thermal conductivity (100 ℃, W/(m.K)) | 0.054 | ≤0.065 |
| Mass water content (%) | 2.56 | ≤7.5 |
| Dimensional stability (%) | 0.9 | ≤1.0 |
| Linear shrinkage (%) | 1.8 | ≤2.0 |
The pre-desiliconized fly ash sediment generated in the second sedimentation tank 4 is sent into an activation calcination reactor 7, the reaction time is 120min, the used activating agent is sodium carbonate, and the mass ratio of the added amount of the sodium carbonate to the pre-desiliconized fly ash sediment is 1.4: 1. After calcination, the activated product is fed to an acid bath 8.
The reaction time in the acid leaching tank 8 is 25min, the used acid leaching solution is 200mL of 1mol/L hydrochloric acid, the residual impurity silicon can be removed in the form of silicic acid colloid by leaching of the hydrochloric acid, after sedimentation and separation in the third sedimentation tank 9, the supernatant is discharged into the ferric hydroxide purification reactor 10, the obtained silica gel precipitate can be used as silica gel drying agent for resource recovery, and the determination indexes of the silica gel precipitate and the national standard silica gel drying agent for packaging (GB 10455-.
TABLE 7 silica gel desiccant determination index comparison for packaging
| Index (I) | Silica gel product | GB 10455-1989 |
| Content (including structural Water,%) | 98.1 | ≥98 |
| pH | 4.1 | 4-8 |
| Specific resistance (omega cm) | 2639 | ≥2000 |
| Loss on drying (%) | 2.4 | ≤2.5 |
The water discharged from the third sedimentation tank 9 enters an iron hydroxide purification reactor 10, the reaction time is 25min, the used iron hydroxide purification agent is sodium hydroxide, the adding amount of the sodium hydroxide is 10g/L, after sedimentation separation in a fourth sedimentation tank 11, the supernatant is discharged into a neutralization reactor 12, and the obtained precipitate is iron hydroxide.
And the effluent of the fourth sedimentation tank 11 enters a neutralization reactor 12, the reaction time is 45min, the used neutralizing agent is hydrochloric acid, the adding amount of the hydrochloric acid is 75g/L, after sedimentation separation in a fifth sedimentation tank 13, the supernatant liquid flows back to an iron hydroxide purification reactor 10, and the obtained precipitate is aluminum hydroxide.
The aluminum hydroxide precipitate generated in the fifth sedimentation tank 13 is discharged into the high-temperature calcination reactor 14, the reaction time is 120min, the calcination temperature is 1100 ℃, the calcination product is high-purity aluminum oxide, and the indexes of the high-purity aluminum oxide are shown in a comparison table 8 with the national standard of aluminum oxide (GB/T24487-2009).
TABLE 8 comparison of alumina measurement indices
| Chemical composition (wt%) | Alumina product | GB/T 24487-2009 |
| Al2O3 | 98.4 | ≥98.4 |
| SiO2 | 0.05 | ≤0.06 |
| Fe2O3 | 0.02 | ≤0.03 |
| Na2O | 0.65 | ≤0.7 |
| Burn and relieve | 1.0 | ≤1.0 |
In addition, the treating agents and the corresponding treating conditions used in the above embodiments can be arbitrarily adjusted within the following ranges (i.e., can be adjusted to any end value or any middle value) according to actual conditions:
the reaction time of the pre-desiliconization treatment is 30-1000 min;
the temperature of the activation calcination is 100-1500 ℃, and the time is 10-500 min;
the temperature of the acid dissolution reaction is 25-100 ℃, and the time is 30-600 min;
the time for purifying the ferric hydroxide is 30-500 min.
The high-temperature calcination temperature is 400-1500 ℃, and the time is 10-300 min;
the pre-desiliconization agent is one or more of sodium hydroxide, calcium oxide or potassium hydroxide, the pre-desiliconization agent is added in the form of solution or slurry, the corresponding mass percent is 5-50%, meanwhile, the corresponding mass percent is 5-1000g of fly ash, the addition amount is 100-50000mL, and the pre-desiliconization agent is preferably calcium hydroxide or sodium hydroxide and is mixed with calcium oxide or calcium hydroxide;
the activating agent is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate, and the mass ratio of the activating agent to the precipitate obtained after the pre-desiliconization is 0.5-3.0;
the acid leaching solution is one or more of hydrochloric acid, sulfuric acid, nitric acid or oxalic acid, the mass percentage is 5-20%, the corresponding mass percentage is 5-1000g of fly ash, and the addition amount of the fly ash is 100-50000 mL;
the iron hydroxide purifying agent is one or more of sodium hydroxide, potassium hydroxide, calcium oxide, sodium bicarbonate or sodium carbonate, the adding amount is 5-100g/L, and 5-100g of the iron hydroxide purifying agent is correspondingly added into every 1L of supernate obtained in the step (3);
the neutralizing agent is one or more of hydrochloric acid, sulfuric acid, nitric acid or oxalic acid, and the adding amount is 5-200 g/L;
in the step (1), supernatant obtained by carrying out solid-liquid separation on the sludge-water mixed solution is returned to an inlet of the pre-desiliconization reactor after desiliconization treatment, the treatment time in the desiliconization treatment is 10-500min, the desiliconization agent is one or more of calcium oxide, calcium hydroxide, calcium chloride or calcium fluoride, and the adding amount is 5-200 g/L.
The embodiments described above are intended to facilitate the understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention according to the disclosure of the present invention.
Claims (10)
1. The system is characterized by comprising a grinding machine, a pre-desiliconization reactor, an activation calcination reactor, an acid leaching reactor, an iron hydroxide purification reactor, a neutralization reactor and a high-temperature calcination reactor which are sequentially connected along the direction of extracting alumina, wherein the pre-desiliconization reactor is further connected with a pre-desiliconization agent doser, the activation calcination reactor is further connected with an activator doser, the acid leaching reactor is further connected with an acid leaching solution doser, the iron hydroxide purification reactor is further connected with an iron hydroxide purification agent doser, and the neutralization reactor is further connected with a neutralizer doser.
2. The system for producing high-purity aluminum oxide from fly ash as a resource as claimed in claim 1, wherein a liquid outlet of the pre-desiliconization reactor is further connected with a calcium silicate purification reactor, the calcium silicate purification reactor is further connected with a desiliconization agent doser, and a liquid outlet of the calcium silicate purification reactor is further connected with the pre-desiliconization reactor in a return manner.
3. The system for producing high-purity alumina from fly ash as a resource as claimed in claim 2, wherein a second sedimentation tank is further arranged between the calcium silicate purification reactor and the pre-desilication reactor.
4. The system for producing high-purity alumina from fly ash as a resource as claimed in claim 1, wherein a screen machine is further arranged between the grinding machine and the pre-desilication reactor.
5. The system for producing high-purity aluminum oxide by recycling fly ash as claimed in claim 4, wherein the coarse powder outlet of the screen machine is also connected back to the inlet of the grinding machine.
6. The system for producing high-purity alumina from fly ash as a resource as claimed in claim 1, wherein a first sedimentation tank is further arranged between the pre-desilication reactor and the activation calcination reactor.
7. The system for producing high-purity aluminum oxide by recycling fly ash as claimed in claim 1, wherein a third sedimentation tank is further arranged between the acid leaching reactor and the ferric hydroxide purification reactor.
8. The system for producing high-purity aluminum oxide by recycling fly ash as claimed in claim 1, wherein a fourth sedimentation tank is further arranged between the iron hydroxide purification reactor and the neutralization reactor.
9. The system for producing high-purity alumina from fly ash as a resource as claimed in claim 1, wherein a fifth sedimentation tank is further arranged between the neutralization reactor and the high-temperature calcination reactor.
10. The system for producing high-purity aluminum oxide from fly ash as a resource as claimed in claim 1, wherein the liquid outlet of the neutralization reactor is also connected with the inlet of the ferric hydroxide purification reactor.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113371745A (en) * | 2021-04-21 | 2021-09-10 | 上海电力大学 | System and method for producing high-purity alumina by recycling fly ash |
| CN115571864A (en) * | 2022-09-05 | 2023-01-06 | 六盘水师范学院 | Method for preparing battery-grade iron phosphate by using high-iron type fly ash as raw material |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113371745A (en) * | 2021-04-21 | 2021-09-10 | 上海电力大学 | System and method for producing high-purity alumina by recycling fly ash |
| CN113371745B (en) * | 2021-04-21 | 2024-03-29 | 上海电力大学 | System and method for producing high-purity alumina by recycling fly ash |
| CN115571864A (en) * | 2022-09-05 | 2023-01-06 | 六盘水师范学院 | Method for preparing battery-grade iron phosphate by using high-iron type fly ash as raw material |
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